"The ability to pinpoint the movements of suspects using public transport before, during or after committing an offence is certainly useful, though it should be emphasised that – as a tool – it can only complement and not replace tried-and-tested investigation methods," he said.

But Dr Legrand said there were "some significant privacy concerns" with access to bus data and many people would be unlikely to welcome the prospect of their private data being available to police.

Associate dean at the University of Wollongong’s international school of information systems and technology, Katina Michael, said it was a violation of citizens' privacy rights for public transport cards to be used in a fashion other than what they were intended for.

"Location data can reveal things about a person that should only be accessible with a warrant," she said.

"Who’s to say that this kind of data will not be demanded en masse and used in ways to model a variety of human behaviour using big data approaches?"

Dr Michael said Canberrans should be "very concerned" that police can access bus-users data without a warrant as part of an evidence-based policing movement.

"I am not saying that police should not use this data if they have gone through the appropriate controls, but warrants are essential to ensure that any device that can be used for tracking a person's whereabouts is used justly and ethically," she said.

Australian Privacy Foundation’s chairman Roger Clarke expressed "serious concerns" for the anonymity of bus users and for the due process of law enforcement when told of the AFP MyWay revelations.

Mr Clarke said the foundation had objected to state transport authorities regarding access to personal data, however they had not contacted the ACT government.

Dr Emmeline Taylor, a senior lecturer with the ANU’s school of criminology, said the AFP access to MyWay data without a warrant reflected a “surveillance creep, where data originally used for one purpose is then used for another without the informed consent of subjects”.

“I'd be concerned about whether the public is fully aware of how their data is being captured, stored and potentially later used,” she said.